This invention relates to a method of processing an antifriction bearing unit for a wheel.
The method described in Official Gazette JP-A-2002-370104 has hitherto been known as a method of processing an antifriction bearing unit for a wheel. This method of processing an antifriction bearing unit for a wheel is such that after an outer race, an inner race and a plurality of rolling elements (rollers, balls) of a roller bearing are put together and the central axis of the antifriction bearing unit is directed vertically, the flange surface of a flange portion formed at the vertically lower end of the outer race is fixed to a fixing table for the antifriction bearing unit, while a spindle fitted in the vertically upper end of the inner race is rotated the flange surface of a flange portion formed at the vertically upper end of the inner race to bring the rotating flange surface into contact with a high-precision processing tool to grind the flange surface of the inner race.
However, the method of processing the antifriction bearing unit as described above has the drawback that, since the rotating flange surface of the inner race is brought into contact with a high-precision processing tool and is ground in a state that the outer race is fixed, the inner race which is rotating is likely to receive a large eccentric load from the high-precision processing tool and be inclined relative to the fixed outer race when the flange surface of the inner race is being ground, resulting in the deformation of the outer or inner races or the rolling elements, or the displacement of the rolling elements leading to the damage of the inner race or the rolling elements.
The necessity of large-scale apparatus for rotating the inner race, such as the spindle mentioned above, in addition to the necessity for fixing the outer race, presents the drawback of adding to the time, labor and cost for processing the antifriction bearing unit.
Further, according to the method of processing the roller bearing unit as described above, it is likely that a clearance may be formed between the inner and outer races and the rolling elements during the grinding of the flange surface of the inner race, and allow the inner race to rotate independently of the outer race, resulting in a lowering in the perpendicularity of the central axis of the roller bearing unit to the flange surface.
Further, the method of processing the roller bearing unit as described above has the drawback that in the event that a protrusion, such as the shank of a bolt, projects from the flange surface of the inner race, the protrusion interferes and makes it difficult to grind the flange surface from which the protrusion projects, and makes it difficult to grind the whole flange surface, since the rotating flange surface of the inner race is brought into contact with a high-precision processing tool and is ground in a state that the outer race is fixed.